Report suggests replacing bridge

A new report recommends the full replacement of the Noxon bridge.

The Sanders County Commissioners hired engineering firm Morrison-Maierle to complete a study on the bridge and provide information on what is needed to rehabilitate the bridge. The study was in process prior to inspectors finding two cracks in the bridge structure in July. The study was completed and presented to the commissioners in August.

“We strongly recommend the County consider a full replacement for the Noxon Bridge,” the study states. “The bridge’s deteriorating conditions and functional limitations pose significant safety risks and hinder community access. Without timely intervention, the bridge’s reliability will continue to decline, jeopardizing the county’s transportation infrastructure.” The study goes on to detail that “while full replacement represents a substantial investment, it offers long-term benefits in safety, functionality and economic well-being.”

The 600-foot Noxon bridge was built in 1922. In 1933, the original timber deck was replaced with a steel deck with an asphalt overlay. In 1998, repairs were made to the bridge including replacing truss members, concrete piers, bearings and adding new approach barriers. “Currently, the bridge is classified as functionally obsolete by the Montana Department of Transportation due to lane and shoulder width limitations,” according to the study. After the repairs this summer, DOT lowered the speed limit on the bridge from 25 miles per hour to 10 mph, and imposed additional weight restrictions.

Morrison-Maeirle’s report noted that inspections identified several concerning issues, including smaller dents, deflections and gouging in the bridge trusses. “The brittle cracking exhibited in the truss along with other defects are concerning. We recommend frequent inspections and addressing these deficiencies as soon as possible.” The study recommends the county “initiate planning for full bridge replacement as soon as possible.”

Morrison-Maierle estimates the cost for full bridge replacement at between $25 and $30 million, based on similar projects within the state, and said the replacement project could take 5-10 years to come to fruition, with construction taking 2 years and including erecting a temporary bridge downstream to maintain traffic flow during construction.

The recommendation would be to lengthen the bridge to 700 feet and widen it to two lanes. The company also provided estimates for deck replacement ranging from $500,000 to $5.5 million, which would address immediate safety concerns, but the study noted the lifespan of a new deck would likely be limited by the overall condition of the bridge itself.

County Commissioner Tony Cox said the report has been sent to officials in the state, as well as to members of Congress representing Montana and federal agencies. “We’re trying to draw as much attention to the project as possible in the hopes that it will become a priority for funding,” Cox said.

MDT established a priority list for bridges that are off the primary MDT system of roadways. The agency identified it as a medium priority bridge, but due to the recent closure and repairs, MDT told Morrison-Maierle that the state could increase the priority of the bridge.

Sen. Jon Tester intends to send a letter next week urging swift completion of the project. “Senator Tester understands that safe and reliable infrastructure is critical for communities like Noxon, which is why he negotiated and passed his bipartisan infrastructure law with five Republicans and four Democrats. Through the infrastructure package, he delivered $45 million annually to the State of Montana for bridge repairs and replacements, and is pushing for the Noxon bridge project to receive the support it needs,” a spokesperson for the Senator stated.